1. Field of the Invention
The present invention relates to an image reading device for obtaining image data by reading light transmitted through or reflected from a frame image recorded on an original.
2. Description of the Related Art
Recent years have seen the appearance of technology in which a frame image recorded on an original such as a photographic film is read photoelectrically by a reading sensor such as a CCD. Image processing, such as enlargement or reduction and various types of correction, is then carried out on the read digital image data, and an image is formed on a recording material using laser light modulated on the basis of the digital image data that has completed the image processing.
In technology such as this, in which a frame image is read digitally using a reading sensor such as a CCD, in order to obtain an accurate image reading, the frame image undergoes a preliminary reading (known as a prescan), and reading conditions (for example, the amount of light to be irradiated onto the frame image, the charge accumulation time of the CCD, and the like) are decided in accordance with the density and the like of the frame image. The frame image is then read once again on the basis of the decided reading conditions (known as a fine scan).
In these image readings, it is common for unevenness in the amount of light to be suppressed by diffusing the illumination light using a diffusion plate before irradiating it onto the film surface so that the entire image surface of the frame image is illuminated uniformly.
If, however, there is a scratch or the like present on the image surface, the light irradiated onto the film surface is scattered by the scratch. Consequently, the problem arises that, because correct detected amounts of light which match the image information cannot be obtained by the reading sensor, variations in the amount of light and the like occur and resultingly image defect portions such as black spots and the like appear on the image.
In order to reduce the effects on an image brought about by scratches on the film surface or by dust or the like present on the optical path between the light source and the film (these will be referred to below generically as xe2x80x9cdefect portionsxe2x80x9d), it is common to provide the above diffusion plate near the film (on the light source side) so as to diffuse the illumination light, and then read the frame image using this diffused light. As a result, scratches are erased optically such that defect portions appearing on the image do not stand out.
Alternatively, technology is also proposed in which an image is read using non-visible light that does not respond to image information of the color wavelengths (i.e. wavelengths of the visible light regions), such as infrared light (IR), so as to detect only the light scattering portions caused by defect portions. The image defect portions caused by the detected defect portions are then corrected by undergoing image processing digitally (electrically), based on image information peripheral to the defect portion.
However, the optical erasing of scratches using the above diffusion plate has the drawback that the scratch erasing capability thereof is not so good as compared with that of image correction using non-visible light, although the processing speed of the optical erasing of scratches is faster than the image correction using non-visible light because detection of defect portions using non-visible light (i.e. image reading) is not carried out in the optical erasing of scratches.
In contrast, electrical image correction using non-visible light enables highly accurate correction compared with optical scratch erasure, however, it has the drawback of a slow processing speed.
Moreover, in conventional electrical correction of an image using non-visible light, a diffusion plate (for suppressing unevenness in the light amounts) is generally positioned on the identical optical path used by the light source for illumination light and the light source for non-visible light, and is used in common by both light sources. As a result, the non-visible light also ends up being diffused by the diffusion plate intended for diffusing the illumination light. The drawback thus arises that the capability of detecting defect portions is reduced.
In consideration of the above, it is a first object of the present invention to provide an image reading device capable of reading an image in accordance with desired print conditions by using different scratch erasure methods for originals. It is a second object of the present invention to improve the defect portion detection performance when electrically correcting an image using non-visible light.
The first aspect of the present invention is an image reading device for reading an image recorded on an original according to predetermined different color wavelengths comprising: a light source for visible light for irradiating light of visible light regions onto a surface of the original in accordance with the color wavelengths so as to read image information of the original; a light source for non-visible light for irradiating light of non-visible light regions onto a surface of the original in order to detect scratching on the original or dust on the optical path; a diffusion member that is provided on an optical path of the light source for visible light and the light source for non-visible light and which makes the amount of light irradiated onto the surface of the original substantially uniform; and an image processing section for correcting the image information based on image defect portion detection information obtained by an image reading using light from the light source for non-visible light.
According to the first aspect, the light source for visible light and the light source for non-visible light are provided and a diffusion member is placed on the optical paths of both these light sources so as to make the amounts of light irradiated onto the surface of an original substantially uniform. In the image processing section, image information read using light from the light source for visible light is corrected, based on image defect portion detection information arising from scratching on the original or dust on the optical path obtained by an image reading using light from the light source for non-visible light.
Therefore, according to the first aspect, it is possible to use either of two types of scratch erasure method. Namely, if priority is to be given to the processing speed, even if the effects of scratching on the image are somewhat obvious, scratch erasure is carried out using diffused light. If priority is to be given to the image quality rather than to the processing speed, scratches are accurately corrected using scratch detection by non-visible light. By differentiating between the scratch control methods in this way, it is possible to read an image in accordance with the desired print conditions.
In the second aspect of the present invention, a preliminary reading (a prescan) of image information of the original is made using light of the light source for visible light and, based on the density of the image (the degree of the density) obtained from the reading, a switch is made between an image reading (scratch erasure) using the diffusion member using light from the light source for visible light, and image correction using light from the light source for non-visible light.
According to the second aspect, it is possible to switch flexibly between two types of scratch erasure method. For example, when the density of the image is high and the image reading speed is slow, by switching from image correction using light from a light source for non-visible light to an optical scratch erasure image reading using a light source for visible light, it is possible to prevent the reading speed from being slowed to an extreme. If, on the other hand, the density of the image is low, it is possible to employ a suitable combination of scratch erasure methods in accordance with the density, such as increasing the accuracy of the scratch erasure by using the two types of scratch erasure method in combination. Namely, in comparison with when the same one of these scratch erasure methods is always used, highly efficient image processing, in which the processing speed is balanced with the scratch erasure effect, can be achieved.
In the third aspect of the present invention, the diffusion member is provided in the vicinity of the original on the side on which each of the types of light is irradiated.
According to the third aspect, by placing the diffusion member in the vicinity of the original, it is possible to suppress loss of light from the light source and to increase the accuracy of the scratch erasure using diffused light.
In the fourth aspect of the present invention, the image reading device comprises a plurality of the diffusion members which each have a different degree of light diffusion and also contains diffusion member switching means which can selectively position the plurality of the diffusion members on the optical path.
According to the fourth aspect, because the image reading device is provided with a plurality of diffusion members which each diffuse light at a different degree (i.e. have a different degree of diffusion), and one of these plurality of diffusion members is selected and placed on the optical path by diffusion member switching means, it is possible to alter the degree of diffusion of light from a light source.
As a result, when scratch erasure is performed using diffused light, which is light from a light source for visible light that has been diffused, it is possible to make a choice between using a diffusion member having a high degree of diffusion and a diffusion member having a low degree of diffusion after considering the balance between processing speed and scratch erasure effect, and it is thus possible to make more precise processing settings. In this way, the available choices of scratch erasure processing are increased enabling a variety of print conditions to be met.
In the fifth aspect of the present invention, image information of the original is preliminarily read using light from the light source for visible light, and the plurality of diffusion members are switched based on image density obtained from the reading.
According to the fifth aspect, in the same way as in the above second aspect, image processing in which a balance is achieved between processing speed and image erasure effect is possible, compared with when processing is performed at a fixed degree of diffusion, by switching between the appropriate diffusion member on the basis of the image density. For example, by using a diffusion member having a low degree of diffusion when the image has a high density, excessive reduction in the amount of light can be prevented, and by using a diffusion member having a high degree of diffusion when the image has a low density, highly accurate scratch erasure can be performed.
In the sixth aspect of the present invention, a diffusion plate having a lower degree of diffusion than a diffusion member used for the light source for visible light does is placed on the optical path when the light source for non-visible light is used.
According to the sixth aspect, light from the light source for non-visible light is weakly diffused, although not to the same extent as light from the light source for visible light. Therefore, it is possible to suppress unevenness (shading) in the amount of light to a certain extent, even when an image is read using light from the light source for non-visible light. Consequently, when, for example, images read using the respective types of light each undergo shading correction, the difference between the shading shape of each image is reduced, and it is possible to suppress color unevenness and the like appearing on the image.
In the seventh aspect of the present invention, the diffusion member is placed only on the optical path of the light source for visible light.
In the eighth aspect of the present invention, the diffusion member is placed by diffusion member placement means on the optical path only when the light source for visible light is being used.
According to the seventh and eighth aspects, because only light from the light source for visible light is diffused by the diffusion means, unevenness in the amount of light when reading information of an original image can be suppressed. Moreover, because light from the light source for non-visible light is irradiated onto an original without being diffused, scattered light portions caused by scratching and the like can be detected even more accurately, thereby improving the image correction processing capability.
In the ninth aspect of the present invention, the image reading device is further provided with light shielding means for selectively shielding the light from the light source for visible light and the light from the light source for non-visible light which is irradiated onto a surface of the original.
According to the ninth aspect, because light from the light source for visible light and the light from the light source for non-visible light are selectively shielded by the shielding means, there is no need to control the turning on or off of each light source and, as a result, a lamp light source such as a halogen lamp or the like can be preferably used in the image reading device.
In the tenth aspect of the present invention, the light source for visible light is a group of light emitting elements comprising a plurality of light emitting elements for generating light in wavelengths different from each other, based on the color wavelengths.
According to the tenth aspect, because the light source for visible light is a group of light emitting elements, it is possible to decrease the amount of heat generated compared with a lamp light source such as a halogen lamp, for example, thereby allowing the light generating efficiency of the light source to be improved.
Further, according to the present aspect, it is possible to form a single light source by combining light emitting elements for visible light and light emitting elements for non-visible light and to switch between visible light and non-visible light by controlling light emission of each type of light emitting elements. Therefore, as a half-mirror or the like for aligning optical axes of the two types of light, the structure of the device as a whole can be made simpler.